Resistive capacitive voltage divider

Transcription

1 Resistive capacitive voltage divider Outdoor operation Oil insulated ROF kv

2 General description Resistive capacitive voltage dividers type ROF (RC divider) are used in high voltage networks within the kv (AC) range. They divide the primary voltage to standardised, equivalent secondary voltage for metering, measuring and protection devices. The active part of the RC divider consists of capacitive and parallel connected resistive dividing elements. The length of the active part extends along the entire insulator length, which results in linear voltage distribution. Both elements are calibrated to each other and provide accurate transient voltage signals from the high voltage side to the low voltage side. The RC divider enables very high frequency bandwidth; even direct voltages (DC) can be measured. As the active part of the RC divider is hermetically sealed, an expansion bellow in the head section compensates volume changes of the oil due to temperature variations. The operating pressure will be visualised by monitoring unit. For voltage levels of 420 kv and higher, field distortions are avoided by using a corona ring around the head of the divider. The secondary elements, like adjustment and overvoltage protection components, are located in the terminal box together with the equivalent burden replications. The cover plate of the terminal box can be opened laterally. The connecting sockets for the measuring cables are located on the bottom side of the terminal box. The connection of the secondary output voltage can either be implemented by analogue via a shielded measuring cable or by optionally digital using a fibre optic cable. The RC dividers are factory calibrated and will be delivered with specified measuring cable. Advantages of resistive capacitive voltage dividers Ferro resonance-free and no saturation effects Secondary output can be operated under short-circuit or no-load conditions AC and DC accuracy class R Measurement of harmonics possible up to 1 MHz Transient signals can be measured Accuracy with harmonics up to 10 khz of ±0.2

3 Design Primary terminal Oil voulume monitoring unit Expansion bellow Composite insulator RC divider active part Possible options Painted metal surfaces SF 6 -Gas insulation Up to 4 secondary terminal outputs Terminal box Burden replication, incl. cable parameters are placed in the terminal box Extended frequency transmission range up to 30 khz Digital measurement signal transmission via fibre-optic cable Recalibration, if changes in secondary measurement system. Ground terminal

4 Highlights Linear voltage distribution High accuracy at frequencies up to 10 khz Simple measurement cable connection The optimised arrangement of the resistive and capacitive elements across the entire insulator length results in excellent voltage distribution. The RC divider shows a perfect performance under transient voltage stresses and under high pollution conditions. The linear voltage distribution prevents the occurrence of external partial discharges. The specially developed design of the active part with resistive and capacitive elements guarantees high measurement accuracy and stability up to the 200th harmonic of the rated system frequency. At the same time, high accuracy and stability in voltage variation (linearity) is achieved, starting from lower voltages up to the overvoltage factor. The terminal box has connecting sockets on the bottom side. The measuring cable can be easily connected without any opening of the terminal box. In case additional measuring cable (transmission cable) is needed, the cable can be plugged into the next free available terminal socket. To do this, the prepared burden adaption must be switched off in the terminal box. The divider is still calibrated and ready for operation.

5 Technical data kv kv Type ROF Standard DIN / IEC / IEEE Highest voltage for equipment (U m ) kv Rated power-frequency withstand voltage kv Rated lightning impulse withstand voltage kv Rated frequency (f r ) Hz DC/16.7 / 50 / 60 Accuracy class 0.1; 0.2; 0.5; 1.0; 3.0 Frequency bandwidth Hz DC / (30000) Burden type R or R // C Burden range 100 kω Rated voltage factors sec / sec / h Temperature range C Type ROF Total height of unit* A mm Height to primary terminal* B mm Depth of unit including terminal box C mm Depth of unit base D mm Width of unit base E mm Distance between screw holes at base F mm Min. creepage distance* mm Approximate weight* kg * with standard composite insulator, creepage distance 25 mm/kv

6 Global presence PFIFFNER Instr. Transformers Ltd 5042 Hirschthal PFIFFNER Technologie Ltd 5042 Hirschthal PFIFFNER Systems Ltd 4303 Kaiseraugst +41 (0) (0) (0) PFIFFNER Deutschland GmbH Itzehoe Germany PFIFFNER Transformatör A.S Akyurt /Ankara Turkey PFIFFNER do Brasil Ltda Itajaí Brazil +49 (0) (0) (0) MGC Moser-Glaser Ltd 4303 Kaiseraugst ALPHA Elektrotechnik Ltd 2560 Nidau +41 (0) (0) This document has been drawn up with the utmost care. We cannot, however, guarantee that it is entirely complete, correct or up-to-date. Copyright PFIFFNER / Subject to change without notice HV MV LV HIGH VOLTAGE MEDIUM VOLTAGE LOW VOLTAGE